Knifes are not banned in the UK. How would we be able to peel the potatoes. What is banned is brandishing a knife in a public space, which would lead to a public order offense. Also carrying a lockable knife with a blade greater than 3 inches in a public space is also considered an offense. I say 'considered' because this must be within a certain context. Carrying a large concealed survival knife without good reason in the middle of the city centre would get you into some trouble with the Police as it may be regarded as an offensive weapon. The same principle can be applied to a golf club or cricket bat. Carrying the same knife in the wilderness, you would have a good enough reason to say you needed the knife for the job it was intended to do, as a survival tool.
The same can be said of if your carrying a crowbar and torch at 3 am in a back alley especially if you are known to be a convicted burglar by the police. It is all about common sense really and he context any offensive weapon can be used in.